The invention lies in the field of fluid line couplings and particularly couplings using push-on fittings. My invention provides a unique locking assembly which insures the leak-proof sealing of couplings utilizing push-on fittings.
When the Ford Motor Company began using push-on fittings with garter-type coil springs on its vehicle air conditioning fluid lines and fuel lines, it created a vehicle service industry problem that until recently could be solved only by buying and installing new Ford-made components. The problem continues to be acute due to the high incidence of failure of the O-rings used to seal the connection between the push-on fitting and the pipe to which it is coupled.
The end of the push-on fitting is flared and sized to fit into a cage which houses a garter-type coiled spring. The fitting is pushed onto the pipe and over the O-rings on the end of the pipe until the flared end of the fitting enters the cage and forces the coil spring over the flared end of the pipe and down to encircle the fitting. The spring now prevents the fitting from being pulled out of the cage. Fluid under pressure is sealed within the line by the O-rings between the pipe and the push-on fitting.
Push-on fittings are used to connect a flexible hose to the condenser, the evaporator, the accumulator and the compressor of the air conditioning system and also for connections to the gasoline tank and the carburetor of the vehicle's fuel system.
The fluid lines of vehicle air conditioning systems conventionally operate with line pressures of at least 100 p.s.i. and, at high ambient temperatures, line pressures of 300 p.s.i. are not uncommon. These pressures put severe strain upon the seal between the push-on fitting and the pipe to which the fitting is coupled.
The high incidence of O-ring failures results from high line pressures and the fact that the push-on fitting is usually on one end of a length of flexible hose. Constant vibration and movement of the flexible hose during running of the vehicle's engine and the vehicle itself forces the fitting to move back and forth transverse to its axis, causing wear and eventual rupture of the seal between the O-rings and the inner surface of the push-on fitting.
My locking assembly holds the push-on fitting in axial alignment with the pipe to which the fitting is coupled and, in addition, puts a 360.degree. inwardly directed pressure on the seal between the O-rings and the inner surface of the fitting.
The assembly includes two major components; namely, an externally threaded or flanged male fitting and a uniquely shaped locking nut. Both the male fitting and the locking nut are axially sawed apart into two mirror-image halves. The male fitting has a thin preferably beveled lip at its front end and its internal diameter equals the outside diameter of the push-on fitting. The locking nut is formed to fit over the cage on the pipe and includes internal threading or a recess which meshes with the external threading or engages with the flange of the male fitting. The two halves of the locking nut each contain two threaded holes running perpendicular to the axis of the nut which, when the halves are fitted together, accommodate two screws to securely join the halves into a locking nut.
My unique locking assembly is used in the following manner: The push-on fitting is coupled to the pipe in the usual way by pushing the flared end of the fitting over the end of the pipe and the O-rings encircling the end of the pipe until the flared end of the fitting enters the cage on the pipe containing the garter-type coil spring. Continued pushing on the fitting will cause the coil spring to expand, pass over the flared end of the fitting and then contract and encircle the fitting. The fitting now cannot be withdrawn from the cage. The fluid such as freon-based R-12 refriderant passing through the pipe and the flexible hose connected to the push-on fitting operating under pressures of 100 p.s.i. or more is sealed only by the O-rings on the end of the pipe.
In order to prevent engine vibration and vehicle movement from eventually rupturing these seals, the two halves of my male fitting are placed around the push-on fitting and the thin lip of the fitting pushed into the cage. The lip forces the coil spring away from the fitting until the forward edge of the male fitting presses against the flange of the push-on fitting. Then the two halves of my locking nut are placed over the cage of the pipe and the nut's threads or recess are engaged with the external threads or flange of the male fitting. Two screws are threaded into the two aligned holes in the locking nut to draw the two halves securely together.